The light of thy body is thy eye. If thy eye be single, thy whole body shall be lightsome. But if thy eye be evil thy whole body shall be darksome. If then the light that is in thee, be darkness: the darkness itself how great shall it be!
Praised be Jesus Christ!
Now and forever. Amen.
Jesus warns us about what we allow into ourselves through our eyes (and by extension, all of our senses). He uses the metaphor of light once again. When we look at the sun, a bright and healthy sun illuminates the earth, and life grows and thrives. However, if that light is blocked off, darkness covers the earth, cold sets in, and life withers and dies.
The word "single" in the quote above is variously translated as "healthy, clear, perfect, sound, good". So, if you were confused by that, this is what He means by it. If your eye is healthy, your body will be filled with light. That is, you can see, the world around you is clear, and you can navigate it without fear of harm.
If your eye is evil, that is, not well, then your body will be filled with darkness. You will be unable to see the world about you, you will walk in fear of harm, and be unable to navigate the world with certainty.
Jesus then says "if the light that is in thee, be darkness: the darkness itself how great shall it be." If you find is strange that Jesus calls "light" "darkness", well you're not alone. I found it odd as well. But there's a reason He does this. Consider Isaiah 5:: Woe to you that call evil good, and good evil: that put darkness for light, and light for darkness: that put bitter for sweet, and sweet for bitter. We can, ourselves, call the darkness light. We can exchange in our own hearts, the light for darkness.
There is a subtle truth that Jesus is alluding to here: there is light, or darkness, that emanates from within, and whatever we have within us, we pursue outside of ourselves, and then draw it back into us, either brightening the light that we already have, or darkening the darkness that is already within us. This is why He says "the darkness itself how great shall it be".
And we observe this don't we? The desires of our hearts, we chase. But if those desires are wicked, then what we allow into our bodies through our eyes (and senses) will also be wicked, and this darkens our hearts further. But if our desires are good, then what we allow in through the senses will also be good, and brighten our hearts all the more.
The warning, then, is this: protect that light, and only allow into your eyes that which is also light, and good, and wholesome, and holy. Otherwise, you way extinguish the light that is within you, and cause your heart to be darkened by evil.
Remember, this teaching is given to us in with the wider context of the treasure of our hearts. Go back to Matthew 6:-21: Lay not up to yourselves treasures on earth: where the rust, and moth consume, and where thieves break through and steal. But lay up to yourselves treasures in heaven: where neither the rust nor moth doth consume, and where thieves do not break through, nor steal. For where thy treasure is, there is thy heart also.
For where thy treasure is, there is thy heart also. Let your treasure be God in heaven. And protect that treasure by protecting your heart, and only allowing into your heart that which is good and holy.
Protect your eyes from the glamour of worldly goods.
Thank you for reading, and God bless you!